Basis of Presentation - Additional Information (Detail)	3 Months Ended			6 Months Ended	9 Months Ended
	Dec. 31, 2021 USD ($) shares	Dec. 31, 2020 USD ($) shares	Sep. 30, 2020 USD ($) shares	Sep. 30, 2021	Dec. 31, 2021 USD ($) Segment shares	Dec. 31, 2020 USD ($) shares	Apr. 30, 2021	Mar. 31, 2021 USD ($) shares	Jul. 23, 2020 $ / shares
Company And Summary Of Significant Accounting Policies [Line Items]
Net proceeds form sale of shares after deducting offering expenses			$ 174,700,000			$ 174,749,000
Revenue, practical expedient, financing component					true
Remaining performance obligations	$ 2,100,000,000				$ 2,100,000,000
Number of reportable segments | Segment					3
Increase (decrease) in unbilled accounts receivable					$ 31,300,000
Decrease in collections in excess of revenues and deferred revenues					35,700,000
Collections in excess of revenues and deferred revenues, recognized revenue	47,700,000	$ 7,600,000			169,700,000	82,200,000
Capitalized interest expense	25,800,000	21,800,000			$ 74,200,000	57,700,000
Operating lease, existence of option to terminate					true
Operating lease, option to terminate, description					some of which include renewal options, and some of which include options to terminate the leases within one year.
Total capitalized costs related to patents	3,500,000				$ 3,500,000			$ 3,500,000
Total capitalized costs related to orbital slots and other licenses	64,100,000				64,100,000			53,800,000
Accumulated amortization of patents, orbital slots and other licenses	5,000,000.0				5,000,000.0			4,400,000
Debt issuance costs capitalized					0	5,100,000
Capitalized costs, net, related to software developed for resale	223,142,000				223,142,000			237,100,000
Capitalized cost related to software development for resale	8,700,000	13,000,000.0			29,600,000	41,500,000
Amortization expense of capitalized software development costs	14,500,000	17,100,000			43,600,000	45,100,000
Self-insurance liability	6,900,000				6,900,000			6,900,000
Repurchase and immediate retirement of treasury shares pursuant to vesting of certain RSU agreements	20,423,000	12,266,000			22,165,000	13,013,000
Stock-based compensation expense	21,400,000	21,700,000			64,676,000	64,967,000
Benefit from income taxes	(3,492,000)	$ (7,008,000)			$ 3,469,000	$ (573,000)
Accounting Standards Update 2019-12 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements					In December 2019, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2019-12, Income Taxes (ASC 740): Simplifying the Accounting for Income Taxes, which is intended to simplify various areas related to accounting for income taxes. ASU 2019-12 removes certain exceptions to the general principles in ASC 740 and also clarifies and amends existing guidance to improve consistent application. The Company adopted the new guidance in the first quarter of fiscal year 2022 on a prospective basis and as a result upon purchase of the remaining 51% interest in EBI from Eutelsat (see Note 12 — Acquisitions for more information), and assertion to permanently reinvest future earnings, the deferred tax liability recorded for EBI’s outside basis difference of $8.1 million was reversed and recorded in the first quarter of fiscal year 2022 as an income tax benefit in the condensed consolidated statements of operations and comprehensive income (loss).
Benefit from income taxes					$ 8,100,000
Accounting Standards Update 2020-01 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements				In January 2020, the FASB issued ASU 2020-01, Investments – Equity Securities (ASC 321), Investments – Equity Method and Joint Ventures (ASC 323) and Derivatives and Hedging (ASC 815). ASU 2020-01 clarifies the interaction of the accounting for equity securities under ASC 321 and investments accounted for under the equity method of accounting under ASC 323, and the accounting for certain forward contracts and purchased options accounted for under ASC 815. The Company adopted the new guidance in the first quarter of fiscal year 2022 on a prospective basis and the guidance did not have a material impact on the Company’s consolidated financial statements and disclosures.
Accounting Standards Update 2020-06 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements					In August 2020, the FASB issued ASU 2020-06, Debt – Debt with Conversion and Other Options (ASC 470-20) and Derivatives and Hedging – Contracts in Entity’s Own Equity (Subtopic 815-40). ASU 2020-06 simplifies the accounting for convertible instruments by removing the beneficial conversion and cash conversion accounting models for convertible instruments and removes certain settlement conditions that are required for contracts to qualify for equity classification. This new standard also simplifies the diluted earnings per share calculations by requiring that an entity use the if-converted method for convertible instruments and requires that the effect of potential share settlement be included in diluted earnings per share calculations when an instrument may be settled in cash or shares. The new standard requires entities to provide expanded disclosures about the terms and features of convertible instruments, how the instruments have been reported in the entity’s financial statements, and information about events, conditions, and circumstances that can affect how to assess the amount or timing of an entity’s future cash flows related to those instruments. The new standard will become effective for the Company beginning in fiscal year 2023, with early adoption permitted. The Company is currently evaluating the impact of this standard on its consolidated financial statements and disclosures.
Accounting Standards Update 2020-08 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements					In October 2020, the FASB issued ASU 2020-08, Codification Improvements to Subtopic 310-20, Receivables – Nonrefundable Fees and Other Costs. ASU 2020-08 clarifies that a company should reevaluate whether a callable debt security is within the scope of ASC paragraph 310-20-35-33 for each reporting period. The Company adopted the new guidance in the first quarter of fiscal year 2022 on a prospective basis and the guidance did not have a material impact on the Company’s consolidated financial statements and disclosures.
Accounting Standards Update 2021-08 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements					In October 2021, the FASB issued ASU 2021-08, Business Combinations (ASC 805): Accounting for Contract Assets and Contract Liabilities from Contracts with Customers. ASU 2021-08 requires contract assets and contract liabilities acquired in a business combination to be recognized in accordance with ASC 606 as if the acquirer had originated the contracts. The new standard will become effective for the Company beginning in fiscal year 2024, with early adoption permitted. The Company is currently evaluating the impact of this standard on its consolidated financial statements and disclosures.
Accounting Standards Update 2021-10 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements					In November 2021, the FASB issued ASU 2021-10, Government Assistance (ASC 832): Disclosures by Business Entities about Government Assistance. ASU 2021-10 requires annual disclosures when an entity accounts for a transaction with a government by applying a grant or contribution accounting model by analogy to other accounting guidance. The new standard will become effective for the Company beginning in fiscal year 2023, with early adoption permitted. The Company is currently evaluating the impact of this standard on its consolidated financial statements and disclosures.
CPE Leased Equipment [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property, equipment and satellites	397,416,000				$ 397,416,000			409,942,000
Accumulated depreciation and amortization	$ 203,800,000				$ 203,800,000			193,700,000
Minimum [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property, equipment and satellites, estimated useful life (years)					2 years
Financing lease, remaining lease term	1 year				1 year
Operating lease, remaining lease term	1 year				1 year
Estimated useful life, years					2 years
Minimum [Member] | Internally Developed Software [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property, equipment and satellites, estimated useful life (years)					3 years
Minimum [Member] | CPE Leased Equipment [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property, equipment and satellites, estimated useful life (years)					4 years
Maximum [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property, equipment and satellites, estimated useful life (years)					38 years
Financing lease, remaining lease term	5 years				5 years
Operating lease, remaining lease term	11 years				11 years
Estimated useful life, years					20 years
Maximum [Member] | Software Development Costs [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Estimated useful life, years					5 years
Maximum [Member] | Internally Developed Software [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property, equipment and satellites, estimated useful life (years)					7 years
Maximum [Member] | CPE Leased Equipment [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property, equipment and satellites, estimated useful life (years)					5 years
RigNet, Inc [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Unbilled accounts receivable contributed by acquisition					$ 7,500,000
EBI Step Acquisition [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Percentage of additional interest in subsidiary acquired							51.00%
Funded Research and Development from Customer Contracts [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Percentage of revenue	24.00%	20.00%			23.00%	23.00%
Operating Segments [Member] | Commercial Networks and Government Systems [Member] | Fixed-price Contract [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Percentage of revenue	91.00%	91.00%			90.00%	88.00%
U.S. Government as an Individual Customer [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Percentage of revenue	24.00%	28.00%			26.00%	30.00%
Other Customers [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Percentage of revenue	76.00%	72.00%			74.00%	70.00%
Unfavorable Regulatory Action [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Accrued reserves	$ 12,100,000				$ 12,100,000			10,300,000
Indemnification Agreement [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Accrued reserves	$ 0				$ 0			$ 0
Common Stock [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Number of shares issued and sold | shares			4,474,559			4,474,559
Stock purchase price per share | $ / shares									$ 39.11
Common stock issued based on the vesting terms of certain restricted stock unit agreements | shares	1,091,363	963,565			1,220,370	1,028,535
Common Stock Held in Treasury [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Shares of common stock outstanding | shares	0				0			0
Purchase of treasury shares pursuant to vesting of certain RSU agreements | shares	393,891	348,629			427,229	365,544
Repurchase and immediate retirement of treasury shares pursuant to vesting of certain RSU agreements	$ 20,400,000	$ 12,300,000			$ 22,200,000	$ 13,000,000.0